This invention relates to methods and apparatuses suitable for maintaining the cleanliness of heat exchangers, a nonlimiting example being condenser units of heating, ventilation, and air conditioning (HVAC) systems.
Condensers are a type of heat exchanger primarily used to transfer heat between two mediums, for example, air and a refrigerant, in various heat transfer systems, including but not limited to space heaters, air conditioners, and automotive radiators. In typical HVAC systems, a compressed refrigerant vapor enters a condenser that serves to condense the refrigerant to its liquid state. In particular, the refrigerant vapor flows through hollow cooling coils or tubes of the condenser, where heat is released from the refrigerant and transferred to the surrounding atmosphere, for example, air drawn through fins in contact with the tubes. Thereafter, the condensed refrigerant, which is cooler but still under pressure, is forced through an expansion valve to form a mist before entering an evaporator where the refrigerant is evaporated to its vapor state before again being compressed. The evaporator draws heat from the surrounding atmosphere, which is thereby cooled. In an HVAC system, the cooled air can be circulated through a room, building, passenger compartment, etc.
Condensers for commercial HVAC systems installed in buildings are often located on the roofs of the buildings. As a result, the heat transfer efficiency of a condenser, and therefore the efficiency of the entire HVAC system, declines over time due to debris and outdoor contaminants becoming entrapped within the condenser's tubes. Such a scenario is depicted in FIG. 1, which represents a condenser assembly 10 comprising at least two sets of tube and fin assemblies 12, each having at least one tube 14 (optionally configured as a coil) contacted by multiple fins 16. Contaminants are represented as including relatively coarse debris 18 and relatively finer particulate debris 20. The condenser assembly 10 can be manually cleaned, though doing so can be difficult, time-consuming, and possibly result in damage to the condenser assembly 10. In addition, and as represented in FIG. 2, it can be difficult to remove the debris 18 and 20 from between the tube and fin assemblies 12. Coarse debris 18 can be particularly difficult to remove, with the result that the remaining coarse debris 18 entraps both coarse and particulate debris 18 and 20 during subsequent operation of the condenser assembly 10.
Another approach involves protecting the condenser assembly 10 with a filter that serves to filter the air being drawn through the condenser assembly 10. Commercial examples of such filters are often constructed of a plastic or rubber-coated nylon or some form of loosely woven plastic fibers, configured as a single-layer or multiple-layer mat that is often very thin, for example, less than one centimeter. Filters of this type can be designed to be cleaned periodically or as needed, though at least annually, and are designed for a service life of roughly ten years. These filter products are typically designed and sized for use with a specific HVAC system.
Existing filter products for HVAC systems have several shortcomings, including cost due to the product being designed for specific HVAC systems, and efficiency and energy losses due to the accumulation of contaminants on the products between cleanings and replacements. In particular, filter products require inspection, cleaning or replacement on a regular basis to ensure that the filter product does not become an upstream obstruction that reduces airflow through the condenser unit. As a result, there is considerable resistance to placing any type of airflow restriction upstream of a condenser unit because of the concern for significantly reduced heat transfer efficiency that will result in increased operation and energy consumption by the HVAC system.